Instrument type tube fittings have become widely popular for both industrial and commercial applications. This is due in part to the fact that all that is required is a wrench to install or remove the tube fitting.
Many of these fittings, especially the 316 stainless steel (SS) tube fittings, are used in hazardous applications. Systems using extremely high gas pressures, toxic media, and flammable liquids commonly use these fittings. These fittings are used, for example, in applications such as nuclear power plants, commercial and military aircraft, natural gas vehicles (NGV), shipping, commercial buildings. This list of applications of these fittings is exemplary only and not intended to be limiting.
Unlike threaded pipe fitting systems and welded tubing and pipe systems, the instrument tube fitting has one big potential problem, and that is that the instrument tube fitting can be easily tampered with either accidently or intentionally such as ordinary vandalism or even acts of terror. Unless careful examination or measurement is done, it is difficult to determine if someone has tampered with a tube fitting connection until it is too late. This is a very undesirable and potentially serious situation.
In cases such as the natural gas vehicle industry, many of these systems are easily accessible by the general public and easy to tamper with. All that is needed is a wrench and very quickly someone can loosen a fitting to create a leak, to cause a blowout of the tube fitting that can cause property damage, etc. Every year dozens of fires and explosions are due to these types of fittings being used and the damage done is so severe that usually there is little to no evidence left as to what caused the tube fitting to fail. Since this type of tube fitting is so reliable, the conclusion drawn is that the cause of these problems is due to someone accidentally or intentionally loosening the fitting.
In recent years a new type of tube fitting is being used to compete with instrument type tube fittings that are very difficult to tamper with. They are made from cylindrical components that are swaged under great pressure and cannot be taken apart. These fittings however create problems whenever a system has to be taken apart for service or other needs. Special equipment and skills are needed for their use and they typically require much more space for installation due to the size of the hydraulic tooling needed to install this type of fitting. Their use is very limited as compared to the instrument type tube fitting that is so popular.
Currently there are over 200,000,000 instrument type tube fittings produced every year and nearly half of these are 316 SS or other similar type materials that are mainly used in hazardous situations. The large number of new installations every year makes it abundantly clear that the concern for making these type tube fittings more resistant to tampering is very important.
Thus a need exists to make the instrument type tube fitting more difficult to tamper with, and to provide a tamper-resistant arrangement that makes the instrument type tube fitting more competitive with these new permanent type tube fittings.